[jdk22] RFR: 8323610: G1: HeapRegion pin count should be size_t to avoid overflows

[Thomas Schatzl]

Hi all,

This pull request contains a backport of commit [8643cc21](https://github.com/openjdk/jdk/commit/8643cc21333c6b51242ed3b9295b25f372244755) from the [openjdk/jdk](https://git.openjdk.org/jdk) repository.

The commit being backported was reviewed by Kim Barrett and Albert Mingkun Yang.

Thanks,
  Thomas

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Commit messages:
 - Backport 8643cc21333c6b51242ed3b9295b25f372244755

Changes: https://git.openjdk.org/jdk22/pull/75/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk22&pr=75&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8323610
  Stats: 12 lines in 5 files changed: 0 ins; 0 del; 12 mod
  Patch: https://git.openjdk.org/jdk22/pull/75.diff
  Fetch: git fetch https://git.openjdk.org/jdk22.git pull/75/head:pull/75

PR: https://git.openjdk.org/jdk22/pull/75